Sanding tool



Aug. 21, 1962 G. L. WILLIAMS SANDING TOOL Filed Aug. 30, 1960 INVENTORQ"L.W L ai GEORGE 31 United States 3,049,840 SANDING TOOL George L.Williams, 250 th St., Santa Monica, Calif. Filed Aug. 30, 1960, Ser. No.52,908 3 Claims. (Cl. 51-147) This invention relates generally towoodworking apparatus and more particularly to an improved power sandingtool preferably designed for home or relatively small work shops forboth rough and fine finishing of woodworking surfaces.

Conventional power operated sanding tools suitable for small work shopuse are generally of two types. First, the disc sander in which acircular disc having one flat surface covered with sandpaper material iscaused to rotate at high speeds. Second, the belt sander in which acontinuous belt is wrapped about spaced parallel rollers and caused tomove continuously in one direction. Both types of power operated sandershave certain advantages peculiar to their particular construction. Onthe other hand, the very nature of their design is such thatconsiderable skill is required for finishing relatively large, flatsmooth surfaces.

In disc type sanders, for example, the outer peripheral surface portionsof the sandpaper disc will move faster than the inner portions and thustend to effect more ma terial removal than the inner portions unlesscareful compensating movements are made. In the case of belt sanders,the weight of the motor driving the belt is usually employed forproviding pressure between the sandpaper itself and the work. The usermust thus carefully guide and control the belt sander as otherwise itwill tend to run away. The restraining action required on the part ofthe operator tends to result in the development of uneven pressuresapplied by the various areas of the belt surface.

With all of the foregoing in mind, it is a primary object of thisinvention to provide a greatly improved power operated sanding tool inwhich many of the above difliculties are overcome.

More particularly, it is an object to provide an improved power operatedsanding tool for finishing surfaces in which a high degree of controlledand uniform pressure may be realized without requiring excessive skillon the part of the operator to the end that very uniformly sandedsurfaces result.

Another important object is to provide an improved power operated sanderwhich is designed for sanding relatively large surface areas such astable or desk tops, all in an automatically controlled manner so thatsubstantially uniform material removal is achieved over the entiresurface to be worked.

Briefly, these and many other objects and advantages of this inventionare attained by employing a basic belt type sander unit in combinationwith a work table structure. In accordance with the invention, the worktable is provided with a cutout in its work surface. The belt sander inturn is movably coupled to the under side of the table and arranged tobe moved partially through the cutout so that the upper sanding surfaceof the belt itself is generally parallel to the top surface of the tableand extends slightly above the top surface. Suitable spring type biasingmeans are employed to bias the sanding belt structure to this latterposition. A suitable motor secured to the under side of the table iscoupled to the sander to drive the belt.

With the above arrangement, a flat surface to be sanded may be invertedand placed on the top flat surface of the table itself over the cutoutportion. The work will thus depress the sanding belt surface slightlyuntil it assumes a flush position with the top surface of the table.

3,049,840 Patented Aug. 21, 1962 The actual sanding operation iseffected by the operator moving the entire work over the top surface ofthe table rather than attempting to manipulate the power sander itself.Thus, uniform pressure between the sanding belt and surface to be sandedis always insured. As a consequence, material removal is uniform overthe particular area of the surface being sanded.

In accordance with a feature of the invention, there is also provided afoot operated control pedal coupled to the sanding belt structureenabling the operator to depress the sander to move it from the cutoutas desired so that careful control of the sanding operation isrealizable at all times.

A better understanding of the invention will be had by now referring tothe preferred embodiment thereof as illustrated in the accompanyingdrawings, in which:

FIGURE 1 is an enlarged cutaway perspective view of the improved sandingtool of this invention; and

FIGURE 2 is a front elevational view considerably reduced in scale ofthe sander shown in FIGURE 1.

Referring to FIGURE 1, the sanding tool comprises a work table 10 havinga fiat surface including a generally rectangular cutout 11. Coupled tothe under side of the table is a sanding belt structure including asanding belt 12, the upper surface of which is arranged to extendthrough the rectangular cutout 11 as shown. Belt 12 is supported by asuitable mounting structure including spaced parallel rollers 13 and 14generally co-extensive with the width of the belt 12 and with thetransverse opposite edges of the cutout 11. The arrangement is such thatrotation of the rollers will cause the belt 12 to move in a directionparallel to the longitudinal edges of the cutout.

The mounting structure further includes frame means supporting therollers 13 and 14 and including flat frame plates 15 secured to suitablesupport bars 16 and 17 extending horizontally beneath the table towardsthe rear edge of the table as shown. The ends of the support barsterminate in a shaft 18 having ends respectively journaled withinsuitable brackets 19 and 20 secured to the under side of the table. Theentire sanding belt mounting means can thus pivot about a horizontalaxis A coincident with the axis of the shaft 18 from a position in whichthe belt is disposed below the table surface free from the cutout 11 toa position in which the top surface of the sanding belt is substantiallyflush with or even extends above the work surface of the table.

Drive power for the sanding belt 12 may be provided through a shaftextension 13' connected to the roller 13 and terminating in a suitabledrive pulley structure 21 supported to the side of the bar 16 as at 22Preferably, the pulley 21 is disposed relatively close to the horizontalpivot axis AA so that it will exhibit minimum movement during pivotingaction of the entire frame structure.

The drive pulley 21 is connected through a drive belt 23 to a powerpulley 24 driven by a suitable motor 25 secured to the under side of thetable as by a flange 26. The drive belt 23 constitutes, in essence, aflexible coupling between the motor and the pulley 21 and willaccommodate a slight twisting resulting from pivoting movement of thebelt structure about the shaft 18.

The sanding belt is normally biased to a position extending partiallythrough the cutout 11 by means of a central downwardly extending flange27 having secured to its lowermost tip biasing springs 28 and 29 asshown best in FIGURE 2. The other ends of the biasing springs 28 and 29are secured to the under side of the table as at 30 and 31 so that theywill exert an upward component of force on the pivoted structure. Alsoconnected to the downwardly extending flange 27 is a line or chain 32connected to a foot-operated pedal 33 so that an operator by depressingthe pedal 33 may pull the pivoted structure downwardly against the forceexerted by the biasing springs 28 and 29.

The operation of the improved sanding tool of this invention will beevident from the foregoing description. Initially, an operator maydepress the pedal 33 and thus pivot the entire sanding belt structureabout the shaft 18 so that the top surface of the sanding belt 12 isbelow the level fiat working surface of the table 10. A work to besanded, such as the top surface of a table or desk, is then inverted andplaced on top of the work table to cover the cutout 11. The operator maythen start the motor 25 and through the medium of the flexible belt 23drive the sanding belt 12. Gradual release of pressure on thefoot-operated pedal 33 will then result in the biasing springs 28 and 29urging the sanding belt upwardly through the cutout to engage the workto be sanded. The pivoting of the structure is such that the top surfaceof the sanding belt will be substantially parallel with the top surfaceof the work table so that the entire exposed area of the belt willengage uniformly the work to be sanded.

The weight of the work to be sanded will be borne principally by the topsurface of the table 10, the only pressure between the sanding surfaceof the belt 12 and the work being provided by the tension biasingsprings 28 and 29. This work pressure will be substantially uniform, andthus even sanding takes place.

In the actual sanding operation, the entire work is continuously movedover the flat surface table 10 preferably in a circular motionmaintaining the grain substantially parallel to the direction of motionof the belt until all of the surfaces have been exposed to the sandingbelt 12. Because of the relatively high speed of the belt compared totransverse movements of the work during the circular motion, the sandingdirection is still maintained substantially parallel to the grain.

While it will be evident that equivalent results could be achieved bymounting the sanding belt structure for translational movement ratherthan pivoted movement, the latter arrangement results in a far simplersructure. It is important, however that in this latter structure thepivoting be relatively remotely located from the sanding belt such asshown in the illustration of FIGURE 1. By providing a relatively largedistance between the pivoting axis and the actual sanding belt, thesmall degree of arcuate movement of the sanding belt to bring thesanding surface flush with the table top results in an operationsubstantially equivalent to a direct up and down translation of thesanding belt. In an actual embodiment, the mounting of the backing platefor the sanding belt is made sufficiently resilient to accommodate anyslight angular misalignment of the top surface of the belt with respectto the flat surface of the work engaged thereby.

Thus, while only one particular embodiment of the invention has been setforth and described, many changes and equivalent means for carrying outsimilar functions will occur to those skilled in the art, such changesand equivalent structures falling clearly within the scope and spirit ofthis invention. The improved sanding tool is therefore not to be thoughtof as limited to the particular example set forth and described inFIGURES l and 2.

What is claimed is:

1. A power sanding tool comprising, in combination: a work table havinga substantially rectangular shaped cutout in its upper surface; acontinuous sanding belt; mounting structure for said sanding beltincluding: spaced parallel rollers for supporting and moving said belt,said rollers being positioned adjacent to and substantially coextensivewith the opposite transverse edges of said cutout respectively formoving said belt in a direction parallel to the longitudinal edges ofsaid cutout; frame means rotatably mounting said rollers and extendingsubstantially horizontally under said table towards the rear of saidtable; pivot means connecting said frame means to the under side of saidtable for swinging movement about a horizontal axis substantiallyparallel to said longitudinal edges of said cutout; a motor secured tothe under side of said table; flexible means coupling said motor to atleast one of said rollers for driving said sanding belt; and biasingmeans connected between said frame means and said table for urging saidrollers and sanding belt upwardly into said cutout so that the uppersurface of said sanding belt is positioned above the surface of saidtable whereby a work to be sanded positioned on said table over saidcutout will depress said sanding belt to a position in which its uppersurface is substantially flush with the surface of said table.

2. A power sanding tool according to claim 1, including a foot operatedpedal means connected to said frame means for applying a downward pullon said frame means to lower the surface of said sanding belt to aposition below the surface of said table.

3. A power sanding tool comprising, in combination: a work table havinga cutout in its upper surface; a continuous sanding belt; spacedparallel rollers for supporting and moving said belt; frame meanssupporting said rollers; pivot means pivoting said frame means to theunder side of said table so that said rollers and sanding belt areswingable as a unit with said frame means from a position below saidcutout upward into said cutout to a position in which the upper surfaceof said sanding belt is above the surface of said table; biasing meansconnected between said table and said frame means for urging said framemeans upwardly; a motor secured to the under side of said table; and apulley belt for transmitting power from said motor to one of saidrollers.

References Cited in the file of this patent UNITED STATES PATENTS

